The providing of high quality image data for visual display is critical to the operation of inspection apparatuses, such as industrial inspection apparatus.
Industrial inspection apparatus are often utilized in a variety of high heat, cold or other stressful working environment, which affect the quality of generated image signals. The quality of image signals is affected by the use of such apparatuses. Inspection apparatuses often are moved quickly into and out of areas to be inspected. The amount of received light received at an inspection apparatus image sensor (often detected as the “brightness” of a captured image) and other operating conditions often vary during periods of such movement.
In many inspection applications, the only light illuminating the area being inspected is light that is emitted by the inspection apparatus. With the inspection apparatus being small, such as in a visual inspection apparatus having an elongated inspection tube, there is a limited amount of light that can be delivered. Small apertures can be incorporated in such devices for achieving a reasonable depth of field. However, the smaller the aperture that is employed, less light can reach an image sensor. Without substantial light reading an image sensor, captured frames of image data captured by an inspection apparatus exhibit a low signal-to-noise ratio.
To compensate for variations in received light varying as a result of movement of an inspection apparatus, imaging parameters related to the operation of the image sensor and the processing of its output signal, such as gain and exposure period can be adjusted. Gain applied to the output signal of an image sensor has been observed to result in production of noisy image signals. When an exposure period is increased to compensate for a reduction in received light, problems of image blur have been noted.